


Within These Halls

by DifficultyXV (XV_ictorious)



Series: Commissions [1]
Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alternate Personality, Biting, Blood, Blood Drinking, Dildos, Explicit Sexual Content, F/F, Hair-pulling, Holy sex, Smut, Strap-Ons, Vaginal Fingering, What do you mean Rhea is Seiros, dragon dildos, fangs
Language: English
Status: Completed
Published: 2020-08-19
Updated: 2020-08-19
Packaged: 2021-03-06 01:48:49
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,014
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25995499
Author URL: https://archiveofourown.org/users/XV_ictorious/pseuds/DifficultyXV
Summary: After returning from a mission for the Knights of Seiros, Catherine is greeted by Rhea and the two of them get to talking. Catherine suggests a similarity between the archbishop and Saint Seiros. This sparks an idea in Rhea's head, and she summons Catherine to the Holy mausoleum with little information. Catherine finds herself in a situation she was unprepared for, yet welcomes it wholeheartedly.
Relationships: Catherine/Rhea (Fire Emblem)
Series: Commissions [1]
Series URL: https://archiveofourown.org/series/2026066
Comments: 4
Kudos: 14





	Within These Halls

As Catherine found herself walking side by side with Lady Rhea, a warm voice entered her ears. “You did well today, Catherine.” She had just returned to the monastery from a routine bandit extermination mission with a small troupe of the Knights of Seiros under her command.

“Please, Lady Rhea. I didn’t do anything special today that I haven’t done hundreds of times before.” She protested the praise out of the desire to not let her ego wander too high, and to keep the expectations of the one she admired most low. But even so, her heart turned aflutter at receiving such a statement from the archbishop. “And besides, did you really need to greet me at the gates for such a minor mission?”

The two approached the reception hall, the evening sun blazed an orange glow around the market. Rhea turned to Catherine, still walking. Her stride was commanding and gave off a powerful presence, one that had Catherine feeling almost helpless. “Nonsense. There is no task that is of no importance. Everything has a purpose, and it is your duty as my most trusted knight to bring peace to the people of Fódlan however you can.” The way her voice floated through the air as if nothing could stop it put Catherine at ease. She couldn’t tell if the heat on her face was from the sun or from her blushing.

“In any case, I’m more than happy to serve you. And thank you for the compliment.” Catherine paused in thought. She’s known Rhea for a long time now, ever since she attended the Officers Academy all those years ago. Though she didn’t properly know her until that accident when she was saved. She reminded her of a certain someone she’d heard stories about. “You know, you have a strong resemblance to Saint Seiros, Lady Rhea.”

Seemingly caught by surprise from the comment, Rhea gasped, almost tripping on the final stair leading to the doors of the reception hall. Flustered, she said, “Do I now? What has drawn you to this conclusion?” She didn’t slow down despite the misstep.

Catherine looked toward the sky, hoping to find the tracks her train of thought had followed before arriving at its destination. “Well, I just think that you’re both very strong-willed and extremely kind, just like Saint Seiros in the legends.” She didn’t seem to think about where she herself was headed before she bumped into the door before it had fully opened. “Agh, who left this door open?”

Rhea, who struggled to hide her smile at seeing Catherine’s pedal blunder, said “Don’t get too caught up in the how and why, now. I was just curious at what made you think to compare me to our most beloved Saint Seiros.”

Shaking off the slip up as if it hadn’t happened, Catherine responded, “It’s not just that. You also look a great deal like her. Just from the illustrations I’ve seen.”

“Really?” Rhea said.

“Yes, really.” Catherine stopped in the middle of the reception hall. “I’d even say that if you dressed in armor just like hers, I wouldn’t be able to tell the two of you apart.”

Rhea halted in response. “Oh?” With her hands clasped in front of her, Rhea stood almost perfectly still. Though Catherine’s familiarity with Rhea’s mannerisms allowed her to notice her fidgeting, almost wiggling, beneath her dress. “Would you like that?”

“W-what?” The question caught her off guard. It was just an off-hand comment. Not something worth dwelling on. Or so she thought. “Even if I did, wouldn’t that be some kind of blasphemy? I’m not the most well versed, but there has to be something against that.”

A long, deep sigh is all the prefaced Rhea’s next statement. She leaned in a little closer to Catherine. “I don’t think that’s something you need to worry about.”

Catherine knew now for certain that the heat in her face was coming from the blood rushing to her cheeks. “Are you serious.”

“Come to the Holy Mausoleum at dusk. There will be something there waiting for you.” She leaned in even closer, just close enough for her breath to brush against Catherine’s ear ever so slightly. “Something I’m sure you’ll enjoy.” Rhea then departed further into the reception hall for a few steps before turning around. “Oh, and you’ll want to remove your armor so it won’t get in the way.”

Completely dumbfounded, Catherine stood still, watching as Rhea walked away with her back turned. Her strides exuded confidence and purpose.  _ What the hell does that mean? _ She tried to come up with some kind of answer to the bizarre request she had been presented with. Before her thoughts wandered for too long, she returned to her room.

Just after sunset, Catherine was compelled to do what she was asked. It was Lady Rhea’s order, after all, no matter how vague or confusing it was. She’d been to the Holy Mausoleum before, but it was no place to go to for a spontaneous meeting. Even still, she couldn’t help but be intrigued by what Lady Rhea told her to do. And so she found herself at the entrance of the Holy Mausoleum, her hands shaking.

She wasn’t supposed to be here, but no one was around to notice her enter. She felt like she did when she was still a student, sneaking around the monastery and getting into all kinds of trouble. But there was something else she felt, too. Something much more adult. She couldn’t quite make sense of what she was feeling, but she still felt something that she had never felt as a teenager. 

She pushed open the massive doors to find the space enclosed by them to be lit only in the far back. That was where Saint Seiros’s grave was.  _ Why is that the only place that has any lighting? _ After her eyes adjusted to the new level of light, she saw something else in the distance. A silhouette. But couldn’t make out any details. As she delved deeper into the Mausoleum, and closer to the grave, she noticed a sharp, wing-like crown atop the silhouette, which stood beside the casket belonging to a certain legendary figure.

“Saint Seiros?”

In a voice so deep that Catherine felt it reverberate in her chest echoing throughout the chamber, the figure before her answered. “That is correct.” With an arm stretched out before her, Seiros beckoned Catherine forward. “Now, come here.”

Without saying a word, Catherine approached, fully captivated by the mysterious figure.

“You must wonder how it is that I’m here before you.” Catherine nodded, her mouth agape. “Well, you mustn’t worry about such trivial matters.” Seiros descended the stairs, adorning a long white dress, not unlike a loincloth. Her muscular legs looked as if they were perfectly sculpted from the finest marble in Fódlan. Just as Catherine noticed her eyes wandering to the lower half of the person claiming to be Seiros, a hand was placed on her shoulder. She tensed at the contact but just as she felt startled, a warm breath brushed her ear as words from a serpentine voice slithered its way in. “Answer me this. How would you like to see just how I and your dearly beloved archbishop truly compare?” As Seiros spoke, she walked around the paralyzed Catherine. A bare hand slid across the back of her neck and she shivered. Was it fear that kept her in place? Anxiety? Perhaps something else? Until the same hand came to grip her face from underneath her chin. “What say you?”

Catherine’s heart was now beating so quickly and intensely, she felt her chest tightening. She knew what Seiros was asking her. She knew what was going to happen if she said yes. And she wanted that more than anything else at that moment. “Lady Seiros. Please. Show me.”

With a beast-like growl, Seiros leaned back and laughed. Then suddenly, she wrapped her hand around Catherine’s neck and leaned in so their foreheads were together. “Good.” That single word was all it took to bring Catherine from being cautious to desperately yearning for everything that was about to come.

The next thing she knew, Catherine felt Seiros slam her against a wall, knocking the air out of her. As she gasped to recover, more words came from Seiros. “Oh, my sweet. This is only the beginning.” Her lips curled into a devious smile. “You had best prepare yourself for what’s to come.” As soon as she spoke the last word, a hand cupped Catherine’s breast over her shirt and Seiros brought her lips to Catherine’s forcefully. The sudden stimulation startled her, but she leaned back as far as she could to let Seiros take her. Take her to places she’s never been. To feel things she’d never felt. Though they had only started, Catherine was eager to see where this would lead.

Seiros squeezed her chest tightly, as if to say  _ As of right now, you belong to me. And me alone. _ Catherine’s breathing grew quicker, shallower from her arousal. She gasped as Seiros laid claim to her body. Then, a ripping sound filled the Mausoleum as Seiros forcefully removed the layer that divided Catherine’s chest from her hand. At first, the chill of the air was all Catherine could focus on but soon, she warmed up as Seiros continued to grope her breasts. Seiros broke off the kiss and left Catherine drooling from desire. But she wouldn’t be left alone. Catherine felt Seiros’s tongue sliding all across her chest and she let out a moan. The sound of her muse’s pleasure drove Seiros to go further as she took a breast in her mouth, biting down. The slight pain felt mystical, and Catherine muttered between breaths, “More.”

“Enjoying yourself? Well, then I’m happy to oblige,” Seiros said just before biting down even harder, evoking an even stronger, deeper moan from Catherine.

As she grew weaker from every stroke of the tongue against her chest, Catherine decided to have a little fun herself. With a cocky grin, and a quick laugh to lead into her words, she said, “Heh, is that all you can do?”

Seiros looked up at her, eyebrows angled. Angry. “You want more do you?” Quickly, Catherine felt her mouth clamped shut by Seiros’s hand against her lips. “Watch what you ask for.” Catherine’s eyes grew wide at the prospect of what would come next, and at the surprise of how domineering Seiros was to her.

A warmth that had been growing between Catherine’s legs was brought to the front of her mind as Seiros slid her hand down her chest to just above her point of arousal. “Is this what you wanted?” Sharp green eyes peered directly through Catherine’s as if she could see directly into her mind. Without any more hesitation, Seiros gripped the waistband of Catherine’s slacks and pulled them to her ankles. She was now fully exposed to the cool air and she shivered at the contrast. “That’s more like it.” With one hand over her mouth, Catherine could make no affirmation nor plea to continue. Not that it mattered, because she would get what she wanted one way or another.

Seiros dragged her fingers all across the lower regions of Catherine’s body. Everywhere but the one spot she wanted them most. She made muffled sounds of desperation, which only amused Seiros. “Be patient,” she said, as she offered her nothing but a quick glance. The pure lust in her eyes would not give her the validation of contact, her gaze was on nothing more than the object of her desire. Instead of a confident smirk that she wore up until now, Seiros’s face was completely focused on getting as close to the point of Catherine’s heat. Which only drove her even more wild. She squirmed under the pressure of Seiros’s grip, trying to get her to finally offer her release as she grew more and more sensitive with each passing moment.

Then, the first finger made contact with her slick bud. Catherine lurched. The feeling of getting exactly the thing she desired was too much for her. “Ah, so you’re that sensitive,” Seiros teased, “I think you’ve waited long enough.” To add a flourish to her words, Seiros slipped a single finger into Catherine’s entrance, bringing her to moan deeply into her hand. She had full control over the knight. And so she put another finger in, and with the two she pushed them in and out of the needy Catherine.

The pleasure of finally being fucked by Seiros’s fingers made Catherine lose control. She tilted her head back, humping those fingers in rhythm as they repeatedly entered her. Deep guttural moans escaped her, trapped behind a warm palm against her lips. Seiros quickened her pace as Catherine eagerly accepted her treatment, pushing farther, deeper, faster into her. As she synced her movements with Seiros’s a heat rose within her as she grew closer to climax. Seiros could sense it as she became more erratic. And as she was reaching her peak, Seiros retracted her fingers, leaving Catherine to hump nothing but the chill air until she settled down.

Seiros finally removed her hand from over Catherine’s mouth, but before she could say anything, a pair of slick fingers slipped between her lips. “You naughty girl. You dirtied my fingers with your filthy lust. Now clean them off for me.” Catherine didn’t know if she felt threatened or horny at those words. Perhaps it was a bit of both. Even still, she did as she was told and licked clean the taste of her arousal from Seiros’s fingers. Once she was satisfied with her performance, Seiros slipped her fingers from Catherine’s mouth, leaving Catherine to gasp for air. “Don’t think I'm quite done with you yet,” Seiros, with her deep voice, taunted. “Now, turn around, hands on the wall, and bend over.”

With no power over herself to talk back or resist, Catherine responded, “Y-yes ma’am,” and assumed the position as she was asked. Once she did so, she heard a fingersnap and a brief flash of green light reflected off the wall.

“Now the real fun begins.” Catherine felt two hands come down on her ass with a loud  _ slap _ that echoed throughout the chamber. Seiros took her flesh in her fists and suddenly, a cylindrical rod pushed against her lower lips. “Mmmh, I think you’re going to enjoy this very much.” The words caused her to shiver as her spine tingled from the thought. And without any time to prepare, her pussy spread as Seiros pushed her dildo in. Catherine moaned as it pushed as deep as it could and Seiros’s hips made contact with her own. “That’s the sound I like to hear.” The ribbed dildo was a texture foreign to her, but it felt good like nothing else ever could. “What say we get going, shall we?”

“Please, Lady Seiros. Have your way with me.” Catherine begged. At this moment, the only thoughts filling her mind were of being made into a personal plaything for the most highly revered saint in the world.

“As you wish.” As if the words ignited a fire, Seiros pulled her hips back and as the dildo rubbed against her walls, Catherine let out another deep groan. Seiros left her little time to comprehend what she was feeling before sliding back into her was more force than before. It took some time to get into a proper rhythm, but as Seiros pushed in and out of Catherine, her mind grew fuzzier and she was only able to respond by pushing back with her own hips. Soon, the hall was filled with the sounds of their flesh colliding and the moans uttered by the pair. Each time Seiros slammed her hips into Catherine’s ass, she evoked a deeper moan more genuine than the last.

After settling into a pace the two were satisfied with, Catherine felt a hand grip her short ponytail. The next moment, her hair was yanked back and she was lifted up against Seiros as she was fucked by her strap-on. The same hand moved to wrap around the front of her neck and Seiros breathed heavily against her skin, sending her eyes rolling back just slightly. The next thing she knew, she felt a pair of sharp teeth plunge into her neck. The pain was unlike anything she’d felt before. It sent a rush of pleasure down her spine. A warm liquid seemed between her skin and where those fangs made their incision. And as quickly as she made her bite, Seiros released Catherine’s neck from her jaw. She then lapped up the stream of blood making its way down Catherine’s back. 

The thought of such an action hadn’t excited her before, but with the feeling of Seiros fucking her harder than anyone had before and the hot breath that came before it, Catherine nearly collapsed from the pleasure. She shivered as Seiros’s tongue glided across her back, drinking her blood. The combination of sensations finally sent her over the edge. “F-fuck. Seiros!” She twitched in place as a wave of pleasure shot through her body from neck to toes. Seiros didn’t stop for anything, as she kept pounding her and bit down on her neck once more, sending another wave through her as if the first orgasm hadn’t happened.

Once she decided she had her fill of toying with Catherine, Seiros pulled out and released her from her grasp. After another snap and another green flash of light, Catherine fell to her knees, struggling to find her breath. She was still weak from the overwhelming sensation of what she just experienced. She turned around to face Seiros, clutching the marks left by her teeth. Seiros stood over her, her long green hair flowing just out of reach, licking her lips of the taste of Catherine’s blood. “Well, now how do you think I compare to that archbishop of yours?”

With heavy breaths, Catherine could only respond with a single word. “Heavenly.”

**Author's Note:**

> Thank you so much for reading! This was a piece commissioned by @gazingatseiros on twitter. I love CathRhea so much and getting the chance to write them again was a blast. I hope you enjoyed it and if you did and want me to write something for you, I have my commissions open here at this link: [Commissions.](https://forms.gle/ay78UWb7D9xGcqgW8) Though I will not be accepting more NSFW commissions for the time being, but feel free to request anything else you'd like!


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